title: Detection of inhibitors of phenotypically drug-tolerant Mycobacterium tuberculosis using an in vitro bactericidal screen.
abstract: Many whole cell screens of chemical libraries currently in use are based on inhibition of bacterial growth. The goal of this study was to develop a chemical library screening model that enabled detection of compounds that are active against drug-tolerant non-growing cultures of Mycobacterium tuberculosis. An in vitro model of low metabolically active mycobacteria was established with 8 and 30 day old cultures of M. smegmatis and M. tuberculosis, respectively. Reduction of resazurin was used as a measure of viability and the assay was applied in screens of chemical libraries for bactericidal compounds. The model provided cells that were phenotypically-resilient to killing by first and second-line clinical drugs including rifampicin. Screening against chemical libraries identified proteasome inhibitors, NSC310551 and NSC321206, and a structurally-related series of thiosemicarbazones, as having potent killing activity towards aged cultures. The inhibitors were confirmed as active against virulent M. tuberculosis strains including multi- and extensively-drug resistant clinical isolates. Our library screen enabled detection of compounds with a potent level of bactericidal activity towards phenotypically drug-tolerant cultures of M. tuberculosis.
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Bassett
authors.forename: Shichun
authors.initials: S
authors.lastname: Lun
authors.forename: William R
authors.initials: WR
authors.lastname: Bishai
authors.forename: Haidan
authors.initials: H
authors.lastname: Guo
authors.forename: Joanna R
authors.initials: JR
authors.lastname: Kirman
authors.forename: Mudassar
authors.initials: M
authors.lastname: Altaf
authors.forename: Ronan F
authors.initials: RF
authors.lastname: O'Toole
mesh_terms: D000995:Antitubercular Agents / Q000302:isolation & purification* / Q000494:pharmacology*; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D004361:Drug Tolerance; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects*; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000502:physiology; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000502:physiology*; D010078:Oxazines / Q000378:metabolism; D010084:Oxidation-Reduction; D013194:Staining and Labeling / Q000379:methods; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000995:Antitubercular Agents; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin